The xenomorphs are among the most fucked up monsters ever created, they fuck you in the most brutal possible way to reproduce. They are a giant twisted hive creature that of pure terror that effectively shrinks you down to an ant and stalks you relentlessly. They. Don't. Stop. Ever.

A survival horror that puts you in an area with a finite amount of intelligent xenomorphs and actually code some half decent AI so they can stalk, retreat and otherwise freak you out by opening doors, shutting off lights etc...

Decent tech and set dressing and you have potential for awesomeness.

An Alien AND Predator game should be even more awesome. There's so much to work from for asymmetrical gameplay.

Left 4 Dead has effectively shown the way. How awesome would an updated AI director be?